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Rip currents: a laboratory study of a rip current in the presence of a submerged reef

Author: Poort, M.C.L.
Mentor: Stive, M.J.F. · Reniers, A.J.H.M. · Fontijn, H.L. · Uijttewaal, W.J.S. · Visser, P.J. · Henriquez, M.
Faculty:Civil Engineering and Geosciences
Type:Master thesis
Date:2007-09-14
Publisher: TU Delft, Civil Engineering and Geosciences, Hydraulic Engineering
Keywords: rip currents · laboratory · submerged reef · meandering · vertical velocity distribution
Rights: (c) 2007 M.C.L. Poort

Detailed laboratory measurements of the wave and current field induced by bi-chromatic waves incident on an artificial surfing reef are presented. Strong wave focussing occurs on the surfing reef. Both PTV and in-situ measurements are reported that show the presence of a strong rip current flowing oblique off-shore.
Observed water level set-up and set-down indicate the locations of feeder currents, driving the rip current. Wave-current interaction between the incoming bi-chromatic waves and the outgoing rip-current are apparent in the measurements. The stochastic character of meandering of the rip current is shown by the variance of the low pass filtered time-averaged local velocities.
The vertical velocity distribution could not be determined reliably due to limitations in the test set-up and measurement devices. The dispersion relationship is utilized to connect the PTV surface measurement with the underlying velocity field obtained by in-situ measurements. The total dataset gives a detailed synoptic view of the wave-current field that can be used for model verification and validation.

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